Polycarbonates are already by themselves self-extinguishable materials. However, they are considered as being still too flammable for a number of applications concerning particularly the building industries, electric appliance industries, and aeronautic industries.
And so, to render them still more fire-resistant, numerous solutions have been proposed.
It is thus that halogenated products have alredy been utilized for this purpose, such as decabromodiphenylether, introduced in the form of an additive, or tetrabromobisphenol A, in the form of a polycondensation agent. However, one thus obtains materials which during their use or in fires are likely to liberate hydrochloric or hydrobromic acids which are particularly corrosive and toxic.
Certain derivatives of phosphorus were then proposed which do not present these drawbacks, such as the esters of phenyl acids or phosphonic xylenes halogenated on the ring. However, it is necessary to incorporate them at such amounts that the mechanical properties of the polycarbonate thus loaded and its ability for conversion are seriously affected. Likewise, the cost becomes prohibitive.
Other additives have also been proposed, such as the alkaline salts of alkyl or arylsulfonic acids, but the compositions obtained are generally translucid or opaque.